1. Field of the Invention
This invention relates to propylene polymers which are excellent in rigidity and heat resistance and have an appropriate melt tension and favorable molding processability and appearance.
2. Description of the Related Art
Because of having the characteristics of being excellent in rigidity, heat resistance, molding properties, transparency and chemical resistance, propylene polymers have attracted public attention and widely used for a number of purposes such as various industrial materials, various containers, daily necessities, films and fibers.
Metallocene catalysts with the use of metallocene transition metal compounds have been widely employed, since these catalysts generally have a high activity and propylene polymers obtained thereby are excellent in stereostructural properties. However, the propylene polymers produced by using metallocene catalysts have a disadvantage of having a small memory effect (ME) due to a narrow molecular weight distribution and thus showing a poor molding processability. ME is a value serving as an indication of the non-Newtonian properties of a resin. In general, a higher ME indicates the wider molecular weight distribution and a tendency toward the more favorable molding properties particularly owing to the effects of high-molecular weight components.
As a method of obtaining a propylene polymer having a large ME, there has been known a method wherein polymerization is performed by using a TiCl3-type catalyst or a specific Ziegler-Natta catalyst carrying magnesium. However, much cold xylene solubles (CXS) occur in this method, which brings about some problems of stickiness and worsening in rigidity and heat resistance. As techniques for improving ME by using metallocene-type catalysts, Japanese Patent Laid-Open No. 255812/1990 and ibid. No. 179776/1994 disclose methods of controlling molecular weight distribution by using two types of complexes (Hf and Zr), while International Patent Publication No. 2001-500176 proposes to broaden molecular weight distribution by using two types of Zr complexes having high stereoregularity. In case where the distribution is about 7 or lower, ME cannot be improved by these methods. Although ME can be improved thereby in a system having a larger molecular weight distribution value, no homogeneous mixture can be obtained, which results in a tendency that the molding appearance is worsened. It is therefore required to solve these problems. Japanese Patent Laid-Open No. 181343/2001 and ibid. No. 294609/2001 propose polymers having Mw/Mn ratios ranging from 6 to 50 and a process for producing the same. Although these polymers have high Mw/Mn ratios, MEs thereof are not so high. This is because these polymers contain less high-molecular weight components having relatively high molecular weight of 1,000,000 or more which are appropriate for improving ME. On the other hand, Japanese Patent Laid-Open No. 288220/2001 proposes single-peak polymers having Mw/Mn values of from 4 to 6. Although high molecular weight contributing to the improvement in ME can be achieved in this polymerization system, hydrogen is fed at once at the early stage and thus the polymerization is carried out in an almost hydrogen-free state as the hydrogen is consumed. As a result, there arises a problem that ME becomes higher in comparison with the Mw/Mn ratio and thus the appearance is worsened. It is therefore required to overcome this problem.
Considering the problems as discussed above, the present invention provides propylene polymers which are not only excellent in rigidity and heat resistance but also contain an appropriate amount of high-molecular weight components with little eluting components and have excellent molding processability.
According to the present invention, it has been found out that the above-described problems can be solved by providing a propylene polymer which is characterized by being excellent in stereoregularity, containing a small amount of low-molecular weight components and a small amount of CXS and yet having a large ME.
Accordingly, the propylene polymer of the present invention, which may be copolymerized with ethylene of 0 to 7% by weight, is characterized by comprising satisfying the following requirements:
(1) a melt flow rate (MFR) measured at 230xc2x0 C. under a 2.16 kg load of from 0.1 to 1000 g/10 min;
(2) an isotactic triad fraction (mm) measured by 13Cxe2x80x94NMR of 99.0% or above;
(3) a Q value (i.e., the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn)) measured by gel permeation chromatography (GPC) of from 2.0 to 6.0;
(4) a relation between MFR measured at 230xc2x0 C. under a 2.16 kg load and a memory effect (ME) measured at 190xc2x0 C. at an orifice diameter of 1.0 mm satisfying the following formula (I):
1.75xe2x89xa7(ME)+0.26xc3x97log(MFR)xe2x89xa71.40xe2x80x83xe2x80x83(I);
and
(5) a relation of the cold xylene solubles at 23xc2x0 C. (CXS, unit: % by weight) satisfying the following formula (II)
CXSxe2x89xa60.5xc3x97[C2]+0.2xc3x97log(MFR)+0.5xe2x80x83xe2x80x83(II)
wherein [C2] represents the ethylene unit content (% by weight) in the polymer.
The present invention is also characterized in that the propylene polymer has been polymerized by using a metallocene catalyst.
The present invention provides novel propylene polymers meeting with the physiological requirements (1) to (5) as described below.
Requirement (1): MFR
The propylene polymer according to the present invention has a melt flow rate (MFR) measured at 230xc2x0 C. under a 2.16 kg load of from 0.1 to 1000 g/10 min. It is unfavorable from the viewpoint of the molding process that MFR is lower than 0.1, since the fluidity of the polymer is extremely worsened in this case. It is also unfavorable that MFR exceeds 1000, since the impact strength of the polymer is extremely lowered in this case.
It is preferable that the MFR ranges from 0.5 to 500. Favorable uses are restricted depending on the MFR level. In case of using in injection molding, it is favorable that MFR ranges from 10 to 300. In case of using in film-molding or sheet-molding, it is favorable that MFR ranges from 0.5 to 10, still preferably from 1.0 to 10.
To obtain a polymer having a low MFR, it is necessary to lessen the amount of hydrogen serving as a molecular weight controlling agent. In case of using hydrogen in a small amount, however, the ununiformity of active species as will be described hereinbelow can be hardly established, which makes it difficult to satisfy the relationship between ME and MFR according to the present invention.
Requirement (2): Stereoregularity
The propylene polymer according to the present invention has an isotactic triad fraction measured by 13Cxe2x80x94NMR in the propylene unit chain moiety made up of head-to-tail bonds (i.e., the ratio of propylene unit triads, in which propylene units are bonded to each other via head-to-tail bonds and the methyl branches in the propylene units are in the same direction, to arbitrary propylene unit triads in the polymer chain) of 99.0% or above, preferably 99.5% or above. The isotactic triad fraction will be sometimes referred to as mm fraction thereinafter.
This isotactic triad fraction (mm fraction) is a value which indicates that the stereostructure of methyl groups in the polypropylene molecular chain is isotactically regulate. A higher value means that the higher extent of the regulation. In case where this value is less than the lower limit as specified above, there arises a problem of poor heat resistance.
The 13Cxe2x80x94NMR spectrum can be measured by the following method. Namely, the 13Cxe2x80x94NMR spectrum is measured by completely dissolving a sample (350 to 500 mg) in a solvent prepared by adding about 0.5 ml of deuterated benzene which is a lock solvent to about 2.0 ml of o-dichlorobenzene in an NMR sample tube of 10 mm in diameter followed by the measurement by the proton complete decoupling method at 130xc2x0 C. The measurement conditions are selected so as to give a flip angle of 65xc2x0 and a pulse interval of 5T1 or longer (wherein T1 stands for the maximum value in the methyl group spin-lattice relaxation times) In a propylene polymer, T1 of methylene group and T1 of methine group are shorter than T1 of methyl group. Thus, the recovery ratios of the magnetization of all carbon atoms become 99% or above under these measurement conditions.
The NMR peaks of the propylene polymer of the present invention are identified in accordance with a publicly known method described in Japanese Patent Laid-Open No.273507/1998.
Namely, the methyl group in the third unit of a propylene unit pentad, in which the chemical shift is bonded via a head-to-tail bond and the methyl branches are in the same direction, is referred to as 21.8 ppm and chemical shifts of other carbon peaks are determined on the basis of this standard. According to this standard, the peak assignable to the methyl group in the second unit of the propylene triad represented by PPP [mm] appears within the range of 21.3 to 22.2 ppm, the peak assignable to the methyl group in the second unit of the propylene triad represented by PPP [mr] appears within the range of 20.5 to 21.3 ppm, and the peak assignable to the methyl group in the second unit of the propylene triad represented by PPP [rr] appears within the range of 19.7 to 20.5 ppm.
Requirement (3): Molecular Weight Distribution
Concerning the molecular weight distribution of the propylene polymer according to the present invention, the Q value (i.e., the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn)) measured by gel permeation chromatography (GPC) is specified as ranging from 2.0 to 6.0. It is unfavorable from the viewpoint of operation that the Q value is lower than 2.0, since the resin pressure is elevated in the process of molding the polymer in this case. It is also unfavorable that the Q value exceeds 6.0, since the molecular distribution shifts toward the low-molecular weight side too and thus low-molecular weight components are increased, thereby worsening the physical properties such as rigidity in this case. The polymer according to the present invention is characterized by essentially containing little low-molecular weight components and CXS components. It is preferable that the Q value ranges from 2.5 to 5.5, still preferably from 3.0 to 5.0.
Requirement (4): Correlation Between MF and MFR
The propylene polymer according to the present invention is characterized in that the correlation between memory effect (ME), which serves as an indication of the content of high-molecular weight components in the polymer, and MFR, which serves as an indication of the average molecular weight of the polymer, is in a specific relationship represented by the following formula (I). ME is an indication relating to the molding properties and surface appearance of a polymer and generally correlates to the molecular weight and molecular weight distribution. The optimum range of ME varies depending on purpose. In the case of films, sheets and injection molding, an excessively small PE generally results in an increase in the resin pressure during molding and thus there arise some problems such as uneven film thickness or flow irregularities in injection molding. On the other hand, it is also unfavorable that the ME is excessively large, since there arise problems in resin uniformity and thus the transparency is worsened or flow becomes irregular from causes different from the case of an excessively small ME. An excessively large ME brings about additional problems such that the broadened molecular weight causes lowering in rigidity due to an increase in the low-molecular weight components and stickiness. From these viewpoints, the polymer according to the present invention has a correlationship between ME and MFR within a specific range while maintaining the molecular weight distribution as described above.
1.75xe2x89xa7(ME)+0.26xc3x97log(MFR)xe2x89xa71.40xe2x80x83xe2x80x83(I).
It is known by experience that ME primarily correlates to MFR. In general, the effects of the high-molecular weight components are strengthened with an increase in molecular weight (i.e., a decrease in MFR). The polymer according to the present invention is characterized by having a relatively large ME with respect to MFR compared with conventionally known uniform polymers. It is known that an appropriately high ME contributes to the achievement of favorable molding properties. Thus, the propylene polymer according to the present invention is excellent in molding properties. It is still preferable that the relationship represented by the following formula (I-1) is satisfied.
1.75xe2x89xa7(ME)+0.26xc3x97log(MFR)xe2x89xa71.45xe2x80x83xe2x80x83(I-1).
It is further preferable that the relationship represented by the following formula (I-2) is satisfied.
1.75xe2x89xa7(ME)+0.26xc3x97log(MFR)xe2x89xa71.55xe2x80x83xe2x80x83(I-2).
Requirement (5): CXS
In the present invention, the propylene polymer may be a copolymer. The (co)polymer according to the present invention is characterized in that the cold xylene solubles (CXS) at 23xc2x0 C., which indicates the low-crystallinity components in the polymer, MFR, which indicates of the polymer molecular weight, and the ethylene unit content [C2] (unit: % by weight), which indicates the polymer crystallinity, satisfy the relationship represented by the following formula (II). In the case of a propylene homopolymer, [C2] in the following formula is 0. It is known by experience that CXS primarily correlates to MFR and ethylene content. In general, a polymer having a smaller molecular weight (i.e., a larger MFR) is the more highly soluble in a solvent and thus has a larger CXS value. With an increase in the ethylene content, the crystallinity of the polymer is lowered and thus the polymer becomes more soluble in water, thereby causing a decrease in the CXS value. In the present invention, the content of the ethylene comonomer is from 0 to 7% by weight, preferably from 0 to 5% by weight. It is preferable that the polymer is a homopolymer.
CXSxe2x89xa60.5xc3x97[C2]+0.2xc3x97log(MFR)+0.5xe2x80x83xe2x80x83(II)
wherein [C2] represents the ethylene unit content (% by weight) in the polymer.
The polymer according to the present invention is characterized by having little CXS. Namely, it contains little low-crystallinity components and low-molecular weight components causing a high stickiness of products, worsening rigidity or heat resistance, etc.
It is still preferable that the polymer satisfies the relationship represented by the following formula (II-1).
CXSxe2x89xa60.5xc3x97[C2]+0.2xc3x97log(MFR)+0.4xe2x80x83xe2x80x83(II-1).
It is further preferable that the polymer satisfies the relationship represented by the following formula (II-2).
CXSxe2x89xa60.5xc3x97[C2]+0.2xc3x97log(MFR)+0.3xe2x80x83xe2x80x83(II-1).
(6): Melting Temperature (Tm)
The propylene polymer according to the present invention is preferably characterized by having a melting temperature Tm (xc2x0 C.) measured by DSC of 120xc2x0 C. or above. In case where the polymer is to be used giving priority to rigidity and heat resistance, the melting temperature can be elevated by lessening the amount of a comonomer to be used in the polymerization and thus lowering the ethylene content in the polymer. In general, a propylene-ethylene random copolymer containing about 5 to 6% by weight of ethylene has a melting temperature of about 120 to 130xc2x0 C. It is preferable that the propylene homopolymer according to the present invention has a polymer melting temperature (Tmh) of 149xc2x0 C. or above, still preferably 155xc2x0 C. or above and particularly preferably 157xc2x0 C. or above. In case of random copolymerization with the ethylene where the melting temperature (Tmr) of the random copolymer satisfies Tmrxe2x89xa6120xc2x0 C. and the relationship Tmrxe2x89xa7149xe2x88x925.5 [E] wherein [E] represents the content (% by weight) of ethylene in the polymer, still preferable that Tmrxe2x89xa7155xe2x88x925.5 [E], and particularly preferably that Tmrxe2x89xa7157xe2x88x925.5 [E].
The propylene polymer according to the present invention may be prepared by an arbitrary process without restriction, so long as a propylene polymer satisfying the above requirements can be obtained thereby. Among all, metallocene catalysts are adequate as a catalyst system to be used in producing the polymer of the present invention and it is preferable to use a specific metallocene catalyst. For example, the propylene polymer can be produced by using the following catalysts.
Component A: at least one metallocene compound selected from the transition metal compounds as will be cited hereinbelow; and
component B: at least one compound selected from the group consisting of ion-exchange layered silicates; optionally together with
component C: an organic aluminum compound.
(Component A)
The transition metal compounds to be used as the component A constituting polymerization catalysts which are favorable in producing the propylene polymer according to the present invention are transition metal compounds represented by the following general formula (1). 
wherein Q represents a linkage group crosslinking two conjugated five-membered cyclic ligands; M represents a metal atom selected from among titanium zirconium and hafnium; X and Y represent each a hydrogen atom, a halogen atom, a hydrocarbyl group, an alkoxyno group, an amino group, a nitrogen-containing hydrocarbyl group, a phosphorus-containing hydrocarbyl group or a silicon-containing hydrocarbyl group bonded to M; R1 and R3 represent each hydrogen, a hydrocarbyl group having 1 to 20 carbon atoms, a halogenated hydrocarbyl group having 1 to 20 carbon atoms, a silicon-containing hydrocarbyl group, a nitrogen-containing hydrocarbyl group, an oxygen-containing hydrocarbyl group, a boron-containing hydrocarbyl group or a phosphorus-containing hydrocarbyl group; and R2s represent each hydrogen, a hydrocarbyl group having 1 to 20 carbon atoms, a halogenated hydrocarbyl group having 1 to 20 carbon atoms, a silicon-containing hydrocarbyl group, a nitrogen-containing hydrocarbyl group, an oxygen-containing hydrocarbyl group, a boron-containing hydrocarbyl group or a phosphorus-containing hydrocarbyl group, preferably an aryl group having 6 to 16 carbon atoms.
Q represents a divalent linkage group crosslinking two conjugated five-membered cyclic ligands and examples thereof include:
(a) a divalent hydrocarbyl group having 1 to 20, preferably 1 to 12 carbon atoms;
(b) a silylene group or an oligosilylene group;
(c) a silylene group or an oligosilylene group having as a substituent a hydrocarbyl group having 1 to 20, preferably 1 to 12 carbon atoms;
(d) a germylene group; or
(e) a germylene group having as a substituent a hydrocarbyl group having 1 to 20 carbon atoms.
Among all, an alkylene group and a silylene group having a hydrocarbyl group as a substituent are preferable.
X and Y may be either the same or different and each independently represents the following groups: (a) hydrogen, (b) a halogen, (c) a hydrocarbyl group having 1 to 20, preferably 1 to 12, carbon atoms, or (d) a hydrocarbyl group having 1 to 20, preferably 1 to 12, carbon atoms and containing oxygen, nitrogen or silicon.
Among all, preferable examples thereof include hydrogen, chlorine, methyl, isobutyl, phenyl, dimethylamido and diethylamido groups, etc.
R1 and R3 represent each hydrogen, a hydrocarbyl group having 1 to 20 carbon atoms, a halogenated hydrocarbyl group having 1 to 20 carbon atoms, a silicon-containing hydrocarbyl group, a nitrogen-containing hydrocarbyl group, an oxygen-containing hydrocarbyl group, a boron-containing hydrocarbyl group or a phosphorus-containing hydrocarbyl group. Specific examples thereof include methyl, ethyl, propyl, butyl, hexyl, octyl, phenyl naphthyl, butenyl and butadienyl groups, etc. In addition to the hydrocarbyl groups, citation may be made, as typical examples thereof, of methoxy, ethoxy, phenoxy, trimethylsilyl, diethylamino, diphenylamino, pyrazolyl, indolyl, dimethylphosphino, diphenylphosphino, diphenylboron and diemthoxyboron groups, etc. containing halogen, silicon, nitrogen, oxygen, boron, phosphorus, etc. Among all, hydrocarbyl groups are preferable and methyl, ethyl, propyl and butyl groups are particularly preferable.
R2s represent each hydrogen, a hydrocarbyl group having 1 to 20 carbon atoms, a halogenated hydrocarbyl group having 1 to 20 carbon atoms, a silicon-containing hydrocarbyl group, a nitrogen-containing hydrocarbyl group, an oxygen-containing hydrocarbyl group, a boron-containing hydrocarbyl group or a phosphorus-containing hydrocarbyl group. Among all, aryl groups having 6 to 16 carbon atoms, more specifically, phenyl, xcex1-naphthyl, xcex2-naphthyl, anthracenyl, phenanthryl, pyrenyl, acenaphthyl, aceantrithrenyl groups, etc. are preferable therefor.
These aryl groups may be substituted by a halogen, a hydrocarbyl group having 1 to 20 carbon atoms, a halogenated hydrocarbyl group having 1 to 20 carbon atoms, a nitrogen-containing hydrocarbyl group, an oxygen-containing hydrocarbyl group, a boron-containing hydrocarbyl group or a phosphorus-containing hydrocarbyl group. Among all, phenyl and naphthyl groups are preferable.
M is a metal selected from among titanium, zirconium and hafnium and hafnium is preferable.
Non-limiting examples of the above-described transition metal compounds are as follows:
1. ethylenebis(2-methyl-4-phenyl-4H-azulenyl)hafnium dichloride,
2. ethylenebis(2-ethyl-4-naphthyl-4H-azulenyl)hafnium dichloride,
3. ethylenebis(2-ethyl-4-(4-chloro-2-naphthyl-4H-azulenyl))hafnium dichloride,
4. ethylenebis,(2-ethyl-4-(2-fluoro-4-biphenyl)-4H-azulenyl)hafnium dichloride,
5. isopropylidenebis(2-ethyl-4-phenyl-4H-azulenyl) hafnium dichloride,
6. dimethylsilylenebis(2-ethyl-4-(4-chloro-2-naphthyl-4H-azulenyl))hafnium dichloride,
7. dimethylsilylenebis(2-ethyl-4-biphenyl-4H-azulenyl) hafnium dichloride,
8. dimethylsilylenebis(2-ethyl-4-(2-fluoro-4-biphenyl-4H-azulenyl)hafnium dichloride,
9. diphenylsilylenebis(2-methyl-4-naphthyl-4H-azulenyl)hafnium dichloride,
10. dimethylgermylenebis(2-ethyl-4-(2-fluoro-4-biphenyl-4H-azulenyl)hafnium dichloride and
11. dimethylsilylenebis(2-ethyl-4-(3-chloro-4-t-butyl-4H-azulenyl))hafnium dichloride.
Among all, particularly preferable compounds include dimethylsilylenebis(2-ethyl-4-(2-fluoro-4-biphenyl)-4H-azulenyl)hafnium dichloride, dimethylsilylenebis(2-ethyl-4-(4-chloro-2-naphthyl-4H-azulenyl)hafnium dichloride and dimethylsilylenebis(2-ethyl-4-(3-chloro-4-t-butyl-4H-azulenyl))hafnium dichloride.
The polymer according to the present invention which is excellent in molding properties and contains less xylene solubles is not a technique common to all metallocenes. For example, it is required to have such a special structure as being capable of forming heterologous active sites differing in hydrogen-dependency in a state of being carried on a clay mineral. Complexes having the azulene skeleton are liable to exert such characteristics. Even in azulene-type compounds, these characteristics can be hardly exhibited in case where the seven-membered ring is hydrogenated. However, these characteristics closely relate to the state of carriers and the method of carrying as will be described hereinafter. It is therefore not essentially required in the present invention to specify the structure of the complex. Accordingly, the above description merely indicates an example of the formation of the polymer according to the present invention.
(Component B)
At least one compound selected from the group consisting of ion-exchange layered silicates to be used as the component B in the present invention is a silicate compound having a crystalline structure in which planes formed by ionic bonds, etc. are piled up in parallel at weak bonding strength and the ion contained therein is exchangeable. Most of ion-exchange layered silicates are produced as the main components of clay minerals in nature. However, these ion-exchange layered silicates are not restricted to natural ones but artificial ones are also usable.
Specific examples of the ion-exchange layered silicate include publicly known layered silicates described in xe2x80x9cNendo Kobutugakuxe2x80x9d, Haruo Shiramizu, Asakura-shoten (1995), etc. It is preferable to use smectites, vermiculites and micas such as montmorillonite, sauconite, beidellite, nontronite, saponite, hectorite, stevensite, bentonite or teaniolite.
Although the component B may be used as such without resort to any special treatment, it is preferable to chemically treat the component B. As the chemical treatment, use may be made of either a surface treatment for eliminating impurities adhering to the surface or a treatment affecting the crystalline structure of the clay. More specifically, examples of the treatment include acid-treatments, alkali-treatment, salt-treatment and organic matter-treatments.
In the present invention, it is preferable to exchange at least 40%, preferablyat least 60%, of the exchangeable cation of the group I metal contained in the ion-exchange layered silicate by a cation dissociated from a salt as will be described hereinafter. The salt to be used in the salt-treatment aiming at the ion exchange is a compound consisting of a cation containing at least one atom selected from the group consisting of the atoms of the groups 1 to 14 and at least one anion selected from the group consisting of halogen atoms, inorganic acids and organic acids. More particularly, it is a compound consisting of a cation containing at least one atom selected from the group consisting of the atoms of the groups 2 to 14 and at least one anion selected from the group consisting of Cl, Br, I, F, PO4, SO4, NO3, CO3, C2O4, ClO4, OOCCH3, CH3COCHCOCH3, OCl2, O(NO3)2, O(ClO4)2, O(SO4), OH, O2Cl2, OCl3, OOCH, OOCCH2CH3, C2H4O4 and C5H5O7.
Specific examples thereof include LiF, LiCl, LiBr, LiI, LiOH, Li2SO4, Li(CH3COO), LiCO3, Li(C6H5O7), LiCHO2, LiC2O4, LiClO4, Li3PO4, CaCl2, CaSO4, CaC2O4, Ca(NO3)2, Ca3(C6H5O7)2, MgCl2, MgBr2, MgSO4, Mg(PO4)2, Mg(ClO4)2, MgC2O4, Mg(NO3)2, Mg(OOCCH3)2, MgC4H4O4, Ti(OOCCH3)2, Ti(CO3)2, Ti(NO3)4, Ti(SO4)2, TiF4, TiCl4, Zr(OOCCH3)4, Zr(CO3)2, Zr(NO3)4, Zr(SO4)2, ZrF4, ZrCl4, ZrOCl2, ZrO(NO3)2, ZrO(ClO4)2, ZrO(SO4), HF(OOCCH3)4, HF(CO3)2, HF(NO3)4, HF(SO4)2, HFOCl2, HFF4, HFCl4, V(CH3COCHCOCH3)3, VOSO4, VOCl3, VCl3, VCl4, VBr3, Cr(CH3COCHCOCH3)3, Cr(OOCCH3)2OH, Cr(NO3)3, Cr(ClO4)3, CrPO4, Cr2(SO4)3, CrO2Cl2, CrF3, CrCl3, CrBr3, CrI3, Mn(OOCCH3)2, Mn(CH3COCHCOCH3)2, MnCO3, Mn(NO3)2, MnO, Mn(ClO4)2, MnF2, MnCl2, Fe(OOCCH3)2, Fe(CH3COCHCOCH3)3, FeCO3, Fe(NO3)3, Fe(ClO4)3, FePO4, FeSO4, Fe2(SO4)3, FeF3, FeCl3, FeC6H5O7, Co(OOCCH3)2, Co(CH3COCHCOCH3)3, CoCO3, Co(NO3)2, CoC2O4, Co(ClO4)3, Co3(PO4)2, CoSO4, CoF2, CoCl2, NiCO3, Ni(NO3)2, NiC2O4, Ni(ClO4)2, NiSO4, NiCl2, NiBr2, Zn(OOCCH3)2, Zn(CH3COCHCOCH32, ZnCO3, Zn(NO3)2, Zn(ClO4)3, Zn3(PO4)2, ZnSO4, ZnF2, ZnCl2, AlF3, AlCl3, AlBr3, AlI3, Al2(SO4)3, Al2(C2O4)3, Al(CH3COCHCOCH3)3, Al(NO3)3, AlPO4, GeCl4, GeBr4 and GeI4.
Among all, compounds prepared by the coexistence of Li salts, Sn salts and Zn salts with acid-treatments or successively subjecting these salts thereto are preferred. As described above with respect to the component (A), the process for selecting the polymer according to the present invention varies depending on the complex, carrier and the method of using hydrogen during the polymerization. Therefore, it is not essentially required in the present invention to specify the method of treating the component (B). The ununiformity (formation of heterologous active sites) occurring in carrying the complex is caused by the formation of sites having different acidities on the clay surface. Owing to the balance between the extent of the ununiformity and the degrees of the easiness in carrying the complex at the respective sites, the PP polymer having a special balance, which is never observed in the conventional polymers, can be produced.
By the acid-treatment, impurities on the surface can be eliminated and, moreover, a part or all of cations such as Al, Fe or Mg in the crystalline structure can be eluted.
It is preferable that the acid to be used in the acid-treatment is selected from among hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid and oxalic acid. Two or more salts and acids may be used in the treatment. Although the conditions for the salt- and acid-treatment are not particularly restricted, it is preferable that the treatment is performed at a salt and acid concentration of from 0.1 to 50% by weight and at a temperature from room temperature to the boiling point for 5 minutes to 24 hours so that at least a part of substance(s) constituting at least one compound selected from the group consisting of the ion-exchange layered silicates can be eluted. The salts and acids are usually employed as an aqueous solution.
These ion-exchange layered silicates usually contain adsorption water and interlayer water. It is preferable in the present invention to use such an ion-exchange layered silicate as the component B after removing these absorption water and interlayer water.
Although the heat treatment method for removing the adsorption water and the interlayer water is not particularly restricted, it is necessary to select such conditions as enabling the complete removal of the interlayer water without causing structural destruction. The heating is performed for 0.5 hour or longer, preferably an hour or longer. In this step, it is preferable that the moisture content of the component B after the treatment is 3% by weight or less, still preferably 1% by weight or less, referring the moisture content achieved after dehydrating at a temperature of 200xc2x0 C. under a pressure of 1 mmHg for 2 hours as to 0% by weight.
As described above, it is still preferable in the present invention to use as the component B an ion-exchange layered silicate having a moisture content of 3% by weight or less which is obtained by treating with salts and/or acids.
It is also preferable to use, as the component B, spherical particles having an average particle diameter of 5 xcexcm or above. A natural substance or a marketed product may be used as such, so long as the particles are spherical. Alternatively, use can be made of particles the shape and diameter of which have been controlled by granulation, classification, fractionation, etc.
Examples of the granulation method to be used herein include stirring granulation and spray granulation. It is also possible to use a marketed product. In the granulation, use may be made of organic matters, inorganic solvents, inorganic salts or various binders.
To prevent fracturing or formation of fine particles in the course of the polymerization, it is desirable that the spherical particles thus obtained has a compressive destruction strength of 0.2 MPa or above, still preferably 0.5 MPa or above. In case where the particles have such a strength, the effect of improving the particle properties can be effectively achieved particularly in performing pre-polymerization.
(Component C)
Examples of the organic aluminum compound to be used as the component C in a preferable polymerization catalyst in the present invention include trialkylaluminums such as trimethylaluminum, triethylaluminum, tripropylaluminum and triisobutylaluminum and halogen- or alkoxy-containing alkylammoniums such as diethylaluminum monochloride and diethylaluminum monomethoxide represented by the following general formula:
AlRaP3xe2x88x92a
wherein R presents a hydrocarbyl group having 1 to 20 carbon atoms; P represents hydrogen, halogen or an alkoxy group; and a is a numerical value satisfying the requirement 0 less than axe2x89xa63. It is also possible to use aluminoxanes such as methylaluminoxane. Among all, a trialkylaluminum is particularly preferable.
 less than Preparation/Use of Catalyst greater than 
The component A, the component B and, if needed, the component C are brought into contact with each other to give a catalyst. The contact may be carried out in the following orders, though the present invention is not restricted thereto. The contact may be performed not only in the step of preparing the catalyst but also in the pre-polymerization of the olefin or in the polymerization of the olefin.
1) The component A is brought into contact with the component B.
2) The component A is brought into contact with the component B and then the component C is added.
3) The component A is brought into contact with the component C and then the component A is added.
4) The component B is brought into contact with the component C and then the component A is added.
Alternatively, the three components may be brought into contact with each other at the same time.
In the contact of these catalyst components or after the contact, a polymer such as polyethylene or polypropylene or an organic oxide such as silica or alumina may coexist or come into contact.
The contact may be carried out in an inert gas or an inert hydrocarbon solvent such as pentane, hexane, heptane, toluene orxylene. The contact temperature is from xe2x88x9220xc2x0 C. to the boiling point of the solvent, particularly preferably from room temperature to the boiling point of the solvent.
After the preparation, the catalyst thus obtained may be used as such without washing with an inert solvent, in particular, a hydrocarbon such as hexane or heptane. Alternatively, it may be washed with sucha solvent before using.
If necessary, the above-described component C may be newly combined therewith. The amount of the component C employed herein is selected so as to give an atomic ratio of the aluminum in the component C to the transition metal in the componnt A of 1:0 to 10,000.
Prior to the polymerization, use can be made of a catalyst prepared by pre-polymerizing an olefin such as ethylene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane or styrene followed by, if needed, washing.
It is preferable to carry out this prepolymerization in an inert solvent under mild conditions. It is desirable that the prepolymerization is performed so that from 0.01 to 1000 g, preferably from 0.1 to 100 g, of the polymer is formed per gram of the solid catalyst.
The polymerization reaction is carried out either in the presence or absence of an inert hydrocarbon such as butane, pentane, hexane, heptane, toluene or cyclohexane or a solvent such a as liquefied xcex1-olefin. The polymerization temperature ranges from xe2x88x9250xc2x0 C. to 250xc2x0 C., while the pressure preferably ranges from atmospheric pressure to about 2000 kgxc2x7f/cm2, though the present invention is not restricted thereto. The polymerization can be performed either by the batch method, the continuous method or the semi-batch method.
By introducing hydrogen as a molecular weight controlling agent into the polymerization system, the molecular weight and the molecular weight distribution can be controlled to give the desired polymer.
In case of combining a specific metallocene catalyst with montmorillonite as the component B among the catalyst systems described in the present invention, an active sites having low hydrogen response compared with the usual metallocene active site is also formed and, in its turn, high-molecular weight components are formed. Thus, the weight-average molecular weight can be controlled while maintaining the high-molecular weight components existing therein even in the presence of hydrogen serving as a molecular weight controlling agent. Thus, themolecular weight distribution Q value can be regulated within a range appropriate for resin molding processability.
Since the Q value also depends on the polymerization temperature and the polymerization pressure, it can be regulated within a desired range by optimizing these factors.
Changes in the hydrogen concentration in the polymerization system with the passage of time largely affect not only the molecular weight of the polymer product but also the distribution thereof. In case of feeding hydrogen at once, for example, it is required to obtain a desired MFR that the initial conditions of feeding hydrogen are determined by taking the shift in the molecular weight of the polymer product accompanying the hydrogen consumption with the passage of time into consideration. However, this is not favorable since the MFR can be controlled but a low-molecular weight polymer is formed in a large amount and exerts undesirable effects on the properties of the product in this case.
Since a metallocene catalyst particularly vigorously consumes hydrogen, the hydrogen concentration varies widely in case of feeding hydrogen exclusively in the early stage. In this case, a low-molecular weight polymer is formed in the early stage and then an ultrahigh-molecular weight polymer is formed in the later stage under hydrogen-free conditions. In case of using a metallocene catalyst capable of forming an ultrahigh-molecular weight polymer under the hydrogen-free conditions, it is sometimes feared that the ME becomes excessively large and thus worsens the molding properties or the appearance of molded articles. Accordingly, it is important to regulate the hydrogen concentration within a specific range in the course of the polymerization. Therefore, it is preferable in the present invention to use a device by which hydrogen can be continuously fed so as to maintain the hydrogen concentration at a constant level throughout the polymerization.
With respect to hydrogen, it is preferable to continuously feed hydrogen so as to maintain the hydrogen concentration in the gas phase in an autoclave at a constant level throughout the polymerization in case of bulk polymerization by the batch method or gas phase polymerization. The hydrogen concentration may be regulated to an arbitrary level from 1 ppm to 10000 ppm.
Also, it is preferable to employ the same methods in continuous polymerization. The hydrogen concentration may be regulated to an arbitrary level from 1 ppm to 10000 ppm too. By using these methods, a desired polymer having the physical properties according to the present invention can be obtained.
Copolymerization may carried out by adding a small amount of an xcex1-olefin (C4 to C6) other than ethylene, so long as the physical properties of the polymer disclosed in the present invention are not damaged thereby. In this case, the (xcex1-olefin may be added in an amount up to 6.0% by mol based on propylene.